The present invention relates to an electrically operated camera shutter with a mechanical control device, and more particularlly to an electrically operated camera shutter permitting automatic control of shutter speed mechanically as well as electronically.
The most important disadvantage of conventional electrically operated shutters is the danger of it being impossible to control shutter speed when an electric cell powder source has discharged. In other words, there is danger of making it impossible to take a picture because an electromagnet actuates the shutter closing member before the shutter opening member is actuated. In order to avoid this disadvantage there has been proposed various methods: a mechanical delaying mechanism can automatically operate if the electromagnet does not actuate; a mechanical delaying mechanism may be previously set so as to make exposure for at least the shortest controllable exposure time, even if the electromagnet is inoperative; and the operation members may be actuated in accordance with a predetermined timing sequence so as to operate at the shortest controllable exposure time independently of the condition of the electromagnet. The first method however has faults: a complex mechanism and accordingly low reliability of operation, great expense of manufacture and others. According to the second and third methods the mechanisms are simplified compared with that of the first method but, owing to mechanical control, exposure time is unstable if its shortest controllable value is preselected to be shorter than, for example, 1/2,000 sec. For increase of the exposure time stability improvement of the precision with which the parts of the stabilization mechanism are manufactured is required, which results in increased cost of manufacture. The choice of the second and third methods for determining the shortest controllable exposure time on the basis of the unstability of mechanical control neglects the fact that the shortest exposure time controllable electromagnetically is more stable, and is a bottle neck against realization of the shortest exposure time required for the desired high speed photography.